Time’s Arrow Traced to Quantum Source

A new theory explains the seemingly irreversible arrow of time while yielding insights into entropy, quantum computers, black holes, and the past-future divide.

Coffee cools, buildings crumble, eggs break and stars fizzle out in a universe that seems destined to degrade into a state of uniform drabness known as thermal equilibrium. The astronomer-philosopher Sir Arthur Eddington in 1927 cited the gradual dispersal of energy as evidence of an irreversible “arrow of time.”

But to the bafflement of generations of physicists, the arrow of time does not seem to follow from the underlying laws of physics, which work the same going forward in time as in reverse. By those laws, it seemed that if someone knew the paths of all the particles in the universe and flipped them around, energy would accumulate rather than disperse: Tepid coffee would spontaneously heat up, buildings would rise from their rubble and sunlight would slink back into the sun.

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Physicists Finally Observe a Link Between Quantum Criticality And Entanglement

We know that the realm of quantum physics is science operating at a mind-bogglingly small scale, thus watching quantum interactions happen is always exciting. Now, physicists have managed to observe billions upon billions of entangled electrons passing through a metal film.

The film is a mix of ytterbium, rhodium and silicon, and is what’s known as a ‘strange metal’, one that doesn’t act as expected at very low temperatures.

“With strange metals, there is an unusual connection between electrical resistance and temperature,” explained physicist Silke Bühler-Paschen from Vienna University of Technology in Austria.

“In contrast to simple metals such as copper or gold, this does not seem to be due to the thermal movement of the atoms, but to quantum fluctuations at the absolute zero temperature.”

These fluctuations represent a quantum criticality – that point between quantum states which are the equivalent of transition between liquids, solids and gases in classical physics; the team says this cascade of electrons is the best evidence yet of a link between quantum criticality and entanglement.

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A ‘spooky’ effect of physics that Einstein couldn’t believe has been photographed for the first time


The first photos of quantum-entangled particles showing a Bell inequality.
Paul-Antoine Moreau et al./Science Advances
  • Albert Einstein‘s work in part led to the prediction of quantum entanglement: the idea that two particles can remain connected across vast distances of space and time.
  • Einstein found the idea absurd and “spooky,” but it has since been proved with countless quantum physics experiments.
  • No one had ever made a photograph using the entanglement of photons (pieces of light) until a research team recently did so with a laser-based experiment.

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